//! A highly customizable changelog generator ⛰️
#![doc(
    html_logo_url = "https://raw.githubusercontent.com/orhun/git-cliff/main/website/static/img/git-cliff.png",
    html_favicon_url = "https://raw.githubusercontent.com/orhun/git-cliff/main/website/static/favicon/favicon.ico"
)]

/// Command-line argument parser.
pub mod args;

/// Custom logger implementation.
pub mod logger;

use std::fs::{self, File};
use std::path::{Path, PathBuf};
use std::time::{SystemTime, UNIX_EPOCH};
use std::{env, io};

use args::{BumpOption, Opt, Sort, Strip};
use clap::ValueEnum;
use git_cliff_core::changelog::Changelog;
use git_cliff_core::commit::{Commit, Range};
use git_cliff_core::config::{CommitParser, Config};
use git_cliff_core::embed::{BuiltinConfig, EmbeddedConfig};
use git_cliff_core::error::{Error, Result};
use git_cliff_core::release::Release;
use git_cliff_core::repo::{Repository, SubmoduleRange};
use git_cliff_core::{DEFAULT_CONFIG, IGNORE_FILE};
use glob::Pattern;

/// Checks for a new version on crates.io
#[cfg(feature = "update-informer")]
pub fn check_new_version() {
    use update_informer::Check;
    let pkg_name = env!("CARGO_PKG_NAME");
    let pkg_version = env!("CARGO_PKG_VERSION");
    let informer = update_informer::new(update_informer::registry::Crates, pkg_name, pkg_version);
    if let Some(new_version) = informer.check_version().ok().flatten() {
        if new_version.semver().pre.is_empty() {
            log::info!("A new version of {pkg_name} is available: v{pkg_version} -> {new_version}",);
        }
    }
}

/// Produces a commit range on the format `BASE..HEAD`, derived from the
/// command line arguments and repository tags.
///
/// If no commit range could be determined, `None` is returned.
fn determine_commit_range(
    args: &Opt,
    config: &Config,
    repository: &Repository,
) -> Result<Option<String>> {
    let tags = repository.tags(
        &config.git.tag_pattern,
        args.topo_order,
        args.use_branch_tags,
    )?;

    let mut commit_range = args.range.clone();
    if args.unreleased {
        if let Some(last_tag) = tags.last().map(|(k, _)| k) {
            commit_range = Some(format!("{last_tag}..HEAD"));
        }
    } else if args.latest || args.current {
        if tags.len() < 2 {
            let commits = repository.commits(None, None, None, config.git.topo_order_commits)?;
            if let (Some(tag1), Some(tag2)) = (
                commits.last().map(|c| c.id().to_string()),
                tags.get_index(0).map(|(k, _)| k),
            ) {
                if tags.len() == 1 {
                    commit_range = Some(tag2.to_owned());
                } else {
                    commit_range = Some(format!("{tag1}..{tag2}"));
                }
            }
        } else {
            let mut tag_index = tags.len() - 2;
            if args.current {
                if let Some(current_tag_index) = repository.current_tag().as_ref().and_then(|tag| {
                    tags.iter()
                        .enumerate()
                        .find(|(_, (_, v))| v.name == tag.name)
                        .map(|(i, _)| i)
                }) {
                    match current_tag_index.checked_sub(1) {
                        Some(i) => tag_index = i,
                        None => {
                            return Err(Error::ChangelogError(String::from(
                                "No suitable tags found. Maybe run with '--topo-order'?",
                            )));
                        }
                    }
                } else {
                    return Err(Error::ChangelogError(String::from(
                        "No tag exists for the current commit",
                    )));
                }
            }
            if let (Some(tag1), Some(tag2)) = (
                tags.get_index(tag_index).map(|(k, _)| k),
                tags.get_index(tag_index + 1).map(|(k, _)| k),
            ) {
                commit_range = Some(format!("{tag1}..{tag2}"));
            }
        }
    }

    Ok(commit_range)
}

/// Process submodules and add commits to release.
fn process_submodules(
    repository: &'static Repository,
    release: &mut Release,
    topo_order_commits: bool,
) -> Result<()> {
    // Retrieve first and last commit of a release to create a commit range.
    let first_commit = release
        .previous
        .as_ref()
        .and_then(|previous_release| previous_release.commit_id.clone())
        .and_then(|commit_id| repository.find_commit(&commit_id));
    let last_commit = release
        .commit_id
        .clone()
        .and_then(|commit_id| repository.find_commit(&commit_id));

    log::debug!("Processing submodule commits in {first_commit:?}..{last_commit:?}");

    // Query repository for submodule changes. For each submodule a
    // SubmoduleRange is created, describing the range of commits in the context
    // of that submodule.
    if let Some(last_commit) = last_commit {
        let submodule_ranges = repository.submodules_range(first_commit, last_commit)?;
        let submodule_commits = submodule_ranges.iter().filter_map(|submodule_range| {
            // For each submodule, the commit range is exploded into a list of
            // commits.
            let SubmoduleRange {
                repository: sub_repo,
                range: range_str,
            } = submodule_range;
            let commits = sub_repo
                .commits(Some(range_str), None, None, topo_order_commits)
                .ok()
                .map(|commits| commits.iter().map(Commit::from).collect());

            let submodule_path = sub_repo.path().to_string_lossy().into_owned();
            Some(submodule_path).zip(commits)
        });
        // Insert submodule commits into map.
        for (submodule_path, commits) in submodule_commits {
            release.submodule_commits.insert(submodule_path, commits);
        }
    }
    Ok(())
}

/// Initializes the configuration file.
pub fn init_config(name: Option<&str>, config_path: &Path) -> Result<()> {
    let contents = match name {
        Some(name) => BuiltinConfig::get_config(name.to_string())?,
        None => EmbeddedConfig::get_config()?,
    };

    let config_path = if config_path == Path::new(DEFAULT_CONFIG) {
        PathBuf::from(DEFAULT_CONFIG)
    } else {
        config_path.to_path_buf()
    };

    log::info!(
        "Saving the configuration file{} to {:?}",
        name.map(|v| format!(" ({v})")).unwrap_or_default(),
        config_path
    );

    fs::write(config_path, contents)?;

    Ok(())
}

/// Processes the tags and commits for creating release entries for the
/// changelog.
///
/// This function uses the configuration and arguments to process the given
/// repository individually.
fn process_repository<'a>(
    repository: &'static Repository,
    config: &mut Config,
    args: &Opt,
) -> Result<Vec<Release<'a>>> {
    let mut tags = repository.tags(
        &config.git.tag_pattern,
        args.topo_order,
        args.use_branch_tags,
    )?;
    let skip_regex = config.git.skip_tags.as_ref();
    let ignore_regex = config.git.ignore_tags.as_ref();
    let count_tags = config.git.count_tags.as_ref();
    let recurse_submodules = config.git.recurse_submodules.unwrap_or(false);
    tags.retain(|_, tag| {
        let name = &tag.name;

        // Keep skip tags to drop commits in the later stage.
        let skip = skip_regex.is_some_and(|r| r.is_match(name));
        if skip {
            return true;
        }

        let count = count_tags.is_none_or(|r| {
            let count_tag = r.is_match(name);
            if count_tag {
                log::debug!("Counting release: {}", name);
            }
            count_tag
        });

        let ignore = ignore_regex.is_some_and(|r| {
            if r.as_str().trim().is_empty() {
                return false;
            }

            let ignore_tag = r.is_match(name);
            if ignore_tag {
                log::debug!("Ignoring release: {}", name);
            }
            ignore_tag
        });

        count && !ignore
    });

    if !config.remote.is_any_set() {
        match repository.upstream_remote() {
            Ok(remote) => {
                if !config.remote.github.is_set() {
                    log::debug!("No GitHub remote is set, using remote: {}", remote);
                    config.remote.github.owner = remote.owner;
                    config.remote.github.repo = remote.repo;
                    config.remote.github.is_custom = remote.is_custom;
                } else if !config.remote.gitlab.is_set() {
                    log::debug!("No GitLab remote is set, using remote: {}", remote);
                    config.remote.gitlab.owner = remote.owner;
                    config.remote.gitlab.repo = remote.repo;
                    config.remote.gitlab.is_custom = remote.is_custom;
                } else if !config.remote.gitea.is_set() {
                    log::debug!("No Gitea remote is set, using remote: {}", remote);
                    config.remote.gitea.owner = remote.owner;
                    config.remote.gitea.repo = remote.repo;
                    config.remote.gitea.is_custom = remote.is_custom;
                } else if !config.remote.bitbucket.is_set() {
                    log::debug!("No Bitbucket remote is set, using remote: {}", remote);
                    config.remote.bitbucket.owner = remote.owner;
                    config.remote.bitbucket.repo = remote.repo;
                    config.remote.bitbucket.is_custom = remote.is_custom;
                }
            }
            Err(e) => {
                log::debug!("Failed to get remote from repository: {:?}", e);
            }
        }
    }
    if args.use_native_tls {
        config.remote.enable_native_tls();
    }

    // Print debug information about configuration and arguments.
    log::trace!("Arguments: {:#?}", args);
    log::trace!("Config: {:#?}", config);

    // Parse commits.
    let commit_range = determine_commit_range(args, config, repository)?;

    // Include only the current directory if not running from the root repository.
    //
    // NOTE:
    // The conditions for including the current directory when not running from the root repository
    // have grown quite complex. This may warrant additional documentation to explain the behavior.
    //
    // Current logic triggers when all of the following are true:
    // - `cwd` is a child of the repository root but not the root itself
    // - `args.repository` is either None or empty
    // - `args.workdir` is None
    // - `include_path` is currently empty
    //
    // Additionally, if `include_path` is already explicitly set, it might be preferable to append.
    let cwd = env::current_dir()?;
    let mut include_path = config.git.include_paths.clone();
    if let Ok(root) = repository.root_path() {
        if cwd.starts_with(&root) &&
            cwd != root &&
            args.repository.as_ref().is_none_or(|r| r.is_empty()) &&
            args.workdir.is_none() &&
            include_path.is_empty()
        {
            let path = cwd.join("**").join("*");
            if let Ok(stripped) = path.strip_prefix(root) {
                log::info!(
                    "Including changes from the current directory: {}",
                    cwd.display()
                );
                include_path = vec![Pattern::new(stripped.to_string_lossy().as_ref())?];
            }
        }
    }

    let include_path = (!include_path.is_empty()).then_some(include_path);
    let exclude_path =
        (!config.git.exclude_paths.is_empty()).then_some(config.git.exclude_paths.clone());
    let mut commits = repository.commits(
        commit_range.as_deref(),
        include_path,
        exclude_path,
        config.git.topo_order_commits,
    )?;
    if let Some(commit_limit_value) = config.git.limit_commits {
        commits.truncate(commit_limit_value);
    }

    // Update tags.
    let mut releases = vec![Release::default()];
    let mut tag_timestamp = None;
    if let Some(ref tag) = args.tag {
        if let Some(commit_id) = commits.first().map(|c| c.id().to_string()) {
            match tags.get(&commit_id) {
                Some(tag) => {
                    log::warn!("There is already a tag ({}) for {}", tag.name, commit_id);
                    tag_timestamp = Some(commits[0].time().seconds());
                }
                None => {
                    tags.insert(commit_id, repository.resolve_tag(tag));
                }
            }
        } else {
            releases[0].version = Some(tag.to_string());
            releases[0].timestamp = Some(
                SystemTime::now()
                    .duration_since(UNIX_EPOCH)?
                    .as_secs()
                    .try_into()?,
            );
        }
    }

    // Process releases.
    let mut previous_release = Release::default();
    let mut first_processed_tag = None;
    let repository_path = repository.root_path()?.to_string_lossy().into_owned();
    for git_commit in commits.iter().rev() {
        let release = releases.last_mut().unwrap();
        let commit = Commit::from(git_commit);
        let commit_id = commit.id.to_string();
        release.commits.push(commit);
        release.repository = Some(repository_path.clone());
        release.commit_id = Some(commit_id);
        if let Some(tag) = tags.get(release.commit_id.as_ref().unwrap()) {
            release.version = Some(tag.name.to_string());
            release.message.clone_from(&tag.message);
            release.timestamp = if args.tag.as_deref() == Some(tag.name.as_str()) {
                match tag_timestamp {
                    Some(timestamp) => Some(timestamp),
                    None => Some(
                        SystemTime::now()
                            .duration_since(UNIX_EPOCH)?
                            .as_secs()
                            .try_into()?,
                    ),
                }
            } else {
                Some(git_commit.time().seconds())
            };
            if first_processed_tag.is_none() {
                first_processed_tag = Some(tag);
            }
            previous_release.previous = None;
            release.previous = Some(Box::new(previous_release));
            previous_release = release.clone();
            releases.push(Release::default());
        }
    }

    debug_assert!(!releases.is_empty());

    if releases.len() > 1 {
        previous_release.previous = None;
        releases.last_mut().unwrap().previous = Some(Box::new(previous_release));
    }

    if args.sort == Sort::Newest {
        for release in &mut releases {
            release.commits.reverse();
        }
    }

    // Add custom commit messages to the latest release.
    if let Some(custom_commits) = &args.with_commit {
        releases
            .last_mut()
            .unwrap()
            .commits
            .extend(custom_commits.iter().cloned().map(Commit::from));
    }

    // Set the previous release if the first release does not have one set.
    if releases[0]
        .previous
        .as_ref()
        .and_then(|p| p.version.as_ref())
        .is_none()
    {
        // Get the previous tag of the first processed tag in the release loop.
        let first_tag = first_processed_tag
            .map(|tag| {
                tags.iter()
                    .enumerate()
                    .find(|(_, (_, v))| v.name == tag.name)
                    .and_then(|(i, _)| i.checked_sub(1))
                    .and_then(|i| tags.get_index(i))
            })
            .or_else(|| Some(tags.last()))
            .flatten();

        // Set the previous release if the first tag is found.
        if let Some((commit_id, tag)) = first_tag {
            let previous_release = Release {
                commit_id: Some(commit_id.to_string()),
                version: Some(tag.name.clone()),
                timestamp: Some(
                    repository
                        .find_commit(commit_id)
                        .map(|v| v.time().seconds())
                        .unwrap_or_default(),
                ),
                ..Default::default()
            };
            releases[0].previous = Some(Box::new(previous_release));
        }
    }

    for release in &mut releases {
        // Set the commit ranges for all releases
        if !release.commits.is_empty() {
            release.commit_range = Some(match args.sort {
                Sort::Oldest => Range::new(
                    release.commits.first().unwrap(),
                    release.commits.last().unwrap(),
                ),
                Sort::Newest => Range::new(
                    release.commits.last().unwrap(),
                    release.commits.first().unwrap(),
                ),
            })
        }
        if recurse_submodules {
            process_submodules(repository, release, config.git.topo_order_commits)?;
        }
    }

    // Set custom message for the latest release.
    if let Some(message) = &args.with_tag_message {
        if let Some(latest_release) = releases
            .iter_mut()
            .filter(|release| !release.commits.is_empty())
            .next_back()
        {
            latest_release.message = Some(message.to_owned());
        }
    }

    Ok(releases)
}

/// Runs `git-cliff`.
///
/// # Example
///
/// ```no_run
/// use clap::Parser;
/// use git_cliff::args::Opt;
/// use git_cliff_core::error::Result;
///
/// fn main() -> Result<()> {
///     let args = Opt::parse();
///     git_cliff::run(args)?;
///     Ok(())
/// }
/// ```
pub fn run<'a>(args: Opt) -> Result<Changelog<'a>> {
    run_with_changelog_modifier(args, |_| Ok(()))
}

/// Runs `git-cliff` with a changelog modifier.
///
/// This is useful if you want to modify the [`Changelog`] before
/// it's written or the context is printed (depending how git-cliff is started).
///
/// # Example
///
/// ```no_run
/// use clap::Parser;
/// use git_cliff::args::Opt;
/// use git_cliff_core::error::Result;
///
/// fn main() -> Result<()> {
///     let args = Opt::parse();
///
///     git_cliff::run_with_changelog_modifier(args, |changelog| {
///         println!("Releases: {:?}", changelog.releases);
///         Ok(())
///     })?;
///
///     Ok(())
/// }
/// ```
pub fn run_with_changelog_modifier<'a>(
    mut args: Opt,
    changelog_modifier: impl FnOnce(&mut Changelog) -> Result<()>,
) -> Result<Changelog<'a>> {
    // Retrieve the built-in configuration.
    let builtin_config = BuiltinConfig::parse(args.config.to_string_lossy().to_string());

    // Set the working directory.
    if let Some(ref workdir) = args.workdir {
        args.config = workdir.join(args.config);
        match args.repository.as_mut() {
            Some(repository) => {
                repository
                    .iter_mut()
                    .for_each(|r| *r = workdir.join(r.clone()));
            }
            None => args.repository = Some(vec![workdir.clone()]),
        }
        if let Some(changelog) = args.prepend {
            args.prepend = Some(workdir.join(changelog));
        }
    }

    // Set path for the configuration file.
    let mut path = args.config.clone();
    if !path.exists() {
        if let Some(config_path) = Config::retrieve_config_path() {
            path = config_path;
        }
    }

    // Parse the configuration file.
    // Load the default configuration if necessary.
    let mut config = if let Some(url) = &args.config_url {
        log::debug!("Using configuration file from: {url}");
        #[cfg(feature = "remote")]
        {
            reqwest::blocking::get(url.clone())?
                .error_for_status()?
                .text()?
                .parse()?
        }
        #[cfg(not(feature = "remote"))]
        unreachable!("This option is not available without the 'remote' build-time feature");
    } else if let Ok((config, name)) = builtin_config {
        log::info!("Using built-in configuration file: {name}");
        config
    } else if path.exists() {
        Config::load(&path)?
    } else if let Some(contents) = Config::read_from_manifest()? {
        contents.parse()?
    } else if let Some(discovered_path) = env::current_dir()?.ancestors().find_map(|dir| {
        let path = dir.join(DEFAULT_CONFIG);
        if path.is_file() { Some(path) } else { None }
    }) {
        log::info!(
            "Using configuration from parent directory: {}",
            discovered_path.display()
        );
        Config::load(&discovered_path)?
    } else {
        if !args.context {
            log::warn!(
                "{:?} is not found, using the default configuration",
                args.config
            );
        }
        EmbeddedConfig::parse()?
    };

    // Update the configuration based on command line arguments and vice versa.
    let output = args.output.clone().or(config.changelog.output.clone());
    match args.strip {
        Some(Strip::Header) => {
            config.changelog.header = None;
        }
        Some(Strip::Footer) => {
            config.changelog.footer = None;
        }
        Some(Strip::All) => {
            config.changelog.header = None;
            config.changelog.footer = None;
        }
        None => {}
    }
    if args.prepend.is_some() {
        config.changelog.footer = None;
        if !(args.unreleased || args.latest || args.range.is_some()) {
            return Err(Error::ArgumentError(String::from(
                "'-u' or '-l' is not specified",
            )));
        }
    }
    if output.is_some() && args.prepend.is_some() && output.as_ref() == args.prepend.as_ref() {
        return Err(Error::ArgumentError(String::from(
            "'-o' and '-p' can only be used together if they point to different files",
        )));
    }
    if let Some(body) = args.body.clone() {
        config.changelog.body = body;
    }
    if args.sort == Sort::Oldest {
        args.sort = Sort::from_str(&config.git.sort_commits, true)
            .expect("Incorrect config value for 'sort_commits'");
    }
    if !args.topo_order {
        args.topo_order = config.git.topo_order;
    }

    if !args.use_branch_tags {
        args.use_branch_tags = config.git.use_branch_tags;
    }

    if args.github_token.is_some() {
        config.remote.github.token.clone_from(&args.github_token);
    }
    if args.gitlab_token.is_some() {
        config.remote.gitlab.token.clone_from(&args.gitlab_token);
    }
    if args.gitea_token.is_some() {
        config.remote.gitea.token.clone_from(&args.gitea_token);
    }
    if args.bitbucket_token.is_some() {
        config
            .remote
            .bitbucket
            .token
            .clone_from(&args.bitbucket_token);
    }
    if args.azure_devops_token.is_some() {
        config
            .remote
            .azure_devops
            .token
            .clone_from(&args.azure_devops_token);
    }
    if let Some(ref remote) = args.github_repo {
        config.remote.github.owner = remote.0.owner.to_string();
        config.remote.github.repo = remote.0.repo.to_string();
        config.remote.github.is_custom = true;
    }
    if let Some(ref remote) = args.gitlab_repo {
        config.remote.gitlab.owner = remote.0.owner.to_string();
        config.remote.gitlab.repo = remote.0.repo.to_string();
        config.remote.gitlab.is_custom = true;
    }
    if let Some(ref remote) = args.bitbucket_repo {
        config.remote.bitbucket.owner = remote.0.owner.to_string();
        config.remote.bitbucket.repo = remote.0.repo.to_string();
        config.remote.bitbucket.is_custom = true;
    }
    if let Some(ref remote) = args.gitea_repo {
        config.remote.gitea.owner = remote.0.owner.to_string();
        config.remote.gitea.repo = remote.0.repo.to_string();
        config.remote.gitea.is_custom = true;
    }
    if let Some(ref remote) = args.azure_devops_repo {
        config.remote.azure_devops.owner = remote.0.owner.to_string();
        config.remote.azure_devops.repo = remote.0.repo.to_string();
        config.remote.azure_devops.is_custom = true;
    }
    if args.no_exec {
        config
            .git
            .commit_preprocessors
            .iter_mut()
            .for_each(|v| v.replace_command = None);
        config
            .changelog
            .postprocessors
            .iter_mut()
            .for_each(|v| v.replace_command = None);
    }
    config.git.skip_tags = config.git.skip_tags.filter(|r| !r.as_str().is_empty());
    if args.tag_pattern.is_some() {
        config.git.tag_pattern.clone_from(&args.tag_pattern);
    }
    if args.tag.is_some() {
        config.bump.initial_tag.clone_from(&args.tag);
    }
    if args.ignore_tags.is_some() {
        config.git.ignore_tags.clone_from(&args.ignore_tags);
    }
    if args.count_tags.is_some() {
        config.git.count_tags.clone_from(&args.count_tags);
    }
    if let Some(include_path) = &args.include_path {
        config
            .git
            .include_paths
            .extend(include_path.iter().cloned());
    }
    if let Some(exclude_path) = &args.exclude_path {
        config
            .git
            .exclude_paths
            .extend(exclude_path.iter().cloned());
    }

    // Process commits and releases for the changelog.
    if let Some(BumpOption::Specific(bump_type)) = args.bump {
        config.bump.bump_type = Some(bump_type);
    }

    // Generate changelog from context.
    let mut changelog: Changelog = if let Some(context_path) = args.from_context {
        let mut input: Box<dyn io::Read> = if context_path == Path::new("-") {
            Box::new(io::stdin())
        } else {
            Box::new(File::open(context_path)?)
        };
        let mut changelog = Changelog::from_context(&mut input, config)?;
        changelog.add_remote_context()?;
        changelog
    } else {
        // Process the repositories.
        let repositories: Vec<Repository> = if let Some(paths) = &args.repository {
            paths
                .iter()
                .map(|p| {
                    let abs_path = fs::canonicalize(p)?;
                    Repository::init(abs_path)
                })
                .collect::<Result<Vec<_>>>()?
        } else {
            let cwd = env::current_dir()?;
            vec![Repository::discover(cwd)?]
        };
        let mut releases = Vec::<Release>::new();
        let mut commit_range = None;
        for repository in repositories {
            // Skip commits
            let mut skip_list = Vec::new();
            let ignore_file = repository.root_path()?.join(IGNORE_FILE);
            if ignore_file.exists() {
                let contents = fs::read_to_string(ignore_file)?;
                let commits = contents
                    .lines()
                    .filter(|v| !(v.starts_with('#') || v.trim().is_empty()))
                    .map(|v| String::from(v.trim()))
                    .collect::<Vec<String>>();
                skip_list.extend(commits);
            }
            if let Some(ref skip_commit) = args.skip_commit {
                skip_list.extend(skip_commit.clone());
            }
            for sha1 in skip_list {
                config.git.commit_parsers.insert(0, CommitParser {
                    sha: Some(sha1.to_string()),
                    skip: Some(true),
                    ..Default::default()
                });
            }

            // The commit range, used for determining the remote commits to include
            // in the changelog, doesn't make sense if multiple repositories are
            // specified. As such, pick the commit range from the last given
            // repository.
            commit_range = determine_commit_range(&args, &config, &repository)?;

            releases.extend(process_repository(
                Box::leak(Box::new(repository)),
                &mut config,
                &args,
            )?);
        }
        Changelog::new(releases, config, commit_range.as_deref())?
    };
    changelog_modifier(&mut changelog)?;

    Ok(changelog)
}

/// Writes the changelog to a file.
pub fn write_changelog<W: io::Write>(
    args: &Opt,
    mut changelog: Changelog<'_>,
    mut out: W,
) -> Result<()> {
    let output = args
        .output
        .clone()
        .or(changelog.config.changelog.output.clone());
    if args.bump.is_some() || args.bumped_version {
        let next_version = if let Some(next_version) = changelog.bump_version()? {
            next_version
        } else if let Some(last_version) =
            changelog.releases.first().cloned().and_then(|v| v.version)
        {
            log::warn!("There is nothing to bump");
            last_version
        } else if changelog.releases.is_empty() {
            changelog.config.bump.get_initial_tag()
        } else {
            return Ok(());
        };
        if let Some(tag_pattern) = &changelog.config.git.tag_pattern {
            if !tag_pattern.is_match(&next_version) {
                return Err(Error::ChangelogError(format!(
                    "Next version ({}) does not match the tag pattern: {}",
                    next_version, tag_pattern
                )));
            }
        }
        if args.bumped_version {
            writeln!(out, "{next_version}")?;
            return Ok(());
        }
    }
    if args.context {
        changelog.write_context(&mut out)?;
        return Ok(());
    }
    if let Some(path) = &args.prepend {
        let changelog_before = fs::read_to_string(path)?;
        let mut out = io::BufWriter::new(File::create(path)?);
        changelog.prepend(changelog_before, &mut out)?;
    }
    if output.is_some() || args.prepend.is_none() {
        changelog.generate(&mut out)?;
    }

    Ok(())
}
